Jerzy Robert Sobiecki

The influence of glow discharge nitriding, oxynitriding and carbonitriding on surface modification of Ti-1Al-1Mn titanium alloy

Recent surface treatment studies show that titanium alloys should have an improved resistance to frictional wear and fatigue strength limit without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface nitrided, oxynitrided and carbonitrided diffusion layers. This paper presents the results of metallographic examinations, corrosion and wear resistance tests, surface chemical composition investigation, as well as rotating and bending fatigue tests. These surface treatments increase the useful properties of the titanium alloy. The influence of treatment time and the thickness of the layers on its properties are also investigated.

The formation of Ti(OCN) layers produced from metal—organic compounds using plasma-assisted chemical vapour deposition

Abstract The paper describes the conditions necessary for producing surface layers on steel from Ti(OiC 3 H 7 ) 4 + H 4 + 2 mixture using plasma-assisted chemical vapour deposition. It presents the results of metallographic and scanning microscopy examinations and of electron probe microanalysis. The hardness, the wear resistance measured by the “three-rollers-taper” technique and the corrosion resistance measured using a potentiodynamic test are also given.

Properties of surface layers produced on the Ti–6Al–3Mo–2Cr titanium alloy under glow discharge conditions

The recent rapid progress in surface treatment techniques requires that titanium alloys should have an improved resistance to frictional wear without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface layers of specified microstructure and phase composition. The paper presents the results of examinations of the structure and properties of surface layers formed on the Ti)6Al)3Mo)2Cr titanium alloy by glow discharge assisted nitriding and modified process known . as carbonitriding characterized by an alteration of the gaseous atmosphere in which the process is conducted . The investigations included: metallographical examinations, determination the phase and chemical composition of the layers, measurements of their corrosion and frictional wear resistance and scratch tests. The carbonitriding process increases the hardness and improves the wear and corrosion resistance compared to the nitriding technique. Q 2000 Elsevier Science B.V. All rights reserved.

The PACVD method for surface layer deposition using a glow discharge in H2+N2+Ti(OC3H7)4

Abstract The paper describes the conditions necessary for producing surface layers from a Ti(OC3H7)4+H2+N2 mixture on steels using the PACVD method. It discusses the results of metallographic and scanning microscopy examinations and of an electron probe microanalysis. The hardnesses and values of the wear resistance measured using the ‘three-rollers taper’ technique are also given.

Influence of stirring conditions on Ni/Al2O3 nanocomposite coatings

The influence of the stirring conditions in the electrolyte on the structure and properties of Ni/Al2O3 nanocomposite coatings was studied. The coatings were produced by electrochemical reduction on a copper substrate in a Watts bath modified by nickel grain inhibitor, cationic surfactant and low concentrated nanometric alumina. The process has been carried out with different types of agitation (mechanical, ultrasonic stirring and with a copper rotating disc electrode). The structures of the produced coatings were characterised by scanning and transmission electron microscopy as well as X-ray diffraction. The influence of Al2O3 particles on the microhardness of composite coatings was also analysed. The adhesion of the composite coatings to the substrate and coefficient of friction were determined by means of the scratch test. The studies have shown that the bath stirring method affects the content and distribution of the alumina, as well as the properties of the produced composite Ni/Al2O3 coatings.

Response of Human Osteoblast-Like Cells and Fibroblasts to Titanium Alloy Nitrided under Glow Discharge Conditions

Cell adhesion to biomaterials and cell proliferation are affected, among others, by the chemical composition and surface microtopography of the biomaterial. These are, in turn, influenced by sterilisation processes. The aim of this study was to evaluate the sensitivity of osteoblasts and fibroblasts to TiN surfaces deprived of an oxide film or with an enhanced oxide film due to sterilisation in plasma or in an autoclave, respectively. Type TiN+T2N+aTi(N) nitrided surface layers were produced under glow discharge conditions and sterilized in plasma Sterrad 100 and in a steam autoclave. The results provide evidence that nitrided surface layers improved wearand corrosion resistance of the titanium alloy and that these features were not influenced by sterilisation procedures that resulted in various oxide films. In vitro study of human fibroblast and osteoblast-like cells cultured on TiN surfaces modified by sterilisation processes showed that cells respond to the presence of an enhanced oxide film by aggregating, exhibiting lower viability and increased apoptosis, while to a surface deprived of oxides, by regular spreading and high viability. It can be concluded that differences in surface composition and topography of the nitrided surface layers due to various types of sterilisation elicit specific cell responses, and plasma sterilisation seems to be optimal for bone implants with this surface layer.

The Use of Trimethylaluminum for Producing Surface Layers by the PACVD Method

The paper presents the use of trimethylaluminum in PACVD method to obtain the surface layers like alumina or aluminum nitride on Inconel nickel alloy. The glow discharge nitriding at a temperature of 750°C leads to the formation of aluminum oxynitride in the layer, whereas annealing in argon plasma at a temperature of 1050°C – to the formation of nickel and aluminum based intermetallic phases of the NiAl or Ni3Al type with aluminum oxide present within the outer zone of the coating. The presence of the surface layer of the Al2O3+NiAl+Ni3Al type formed on nickel alloys may be significant from the point of view of the applications that require a high heat resistance.

Properties of composite Ti(NCO) layers formed on tool steel under glow discharge conditions

Recently, metallo-organic compounds have become the donors of titanium in the PACVD process because a chlorine atmosphere is to be avoided. A Ti(NCO) layer was formed on tool steel by using titanium tetraisopropoxide, hydrogen and nitrogen under glow discharge conditions. This process was combined with the plasma nitriding process to obtain composite Ti(NCO) layers on tool steel. The layers thus obtained had high hardness, good wear and corrosion-resistant properties. Detailed results on the structure and properties of this layer are presented.

Corrosion Properties of Oxide Layers Produced on Titanium Nitride by Means of Plasma Electrolytic Oxidation of Various Duration

The corrosion resistance of oxide layers produced on titanium nitride (obtained in glow-discharge nitriding) by means of electrolytic oxidation at different potentials and durations is presented in the paper. The oxidation processes were carried out in phosphoric acid (V) (25wt.%) containing Ca2+ calcium ions. Two plasma oxidation potentials of 40 V and 100 V were applied. Treatment was carried out at two different process durations, i.e. 30 minutes and 120 minutes. The impact of oxidation potential and process time on the morphology of the surface and corrosion properties of the oxide layers obtained was examined.

Corrosion Properties of Plasma Oxidized Titanium Nitride for Biomedical Applications

The article compares the corrosion properties of oxide layers formed on titanium nitride (obtained in glow-discharge nitriding) using electrolytic plasma oxidation. The corrosion properties are analysed in correlation with the surface morphology, microstructure and chemical composition of the layers. The oxidation processes were carried out in 10% and 25% phosphoric acid (V) solutions containing Ca2+ calcium ions. In each of these environments, oxide layers were formed using three oxidation potentials: 200V, 400V and 600 V. The oxidation potential and the concentration of acid and calcium ions in the oxidation solution was shown to affect the morphology of the surface and the corrosion properties of the oxide layers obtained.